End cap for primary windings

ABSTRACT

End caps for the primary winding of an instrument transformer have a radius to relieve the electrical stress at the sharp edges of the primary. The end caps are provided with recesses to receive the primary leads and also have other recesses for locating the primary in a mold for encapsulating the instrument transformer. Lugs or tongues are provided at the inner edge of the end caps to support the winding during molding. Prior to molding, a conducting tape is attached to one primary lead and wound around the end caps.

United States Patent 1 [11] 3,925,744

Canney 5] Dec. 9, 1975 [54] END CAP FOR PRIMARY WINDINGS Inventor: Robert S. Canney, Berwick, Maine Assignee: General Electric Company,

Schenectady, NY.

Filed: Nov. 13, 1974 Appl. No.: 523,255

US. Cl 336/84; 174/138 R; 336/96; 336/209; 336/229 Int. Cl. H01F 15/04; HOlF 27/28 Field of Search 336/84, 96, 90, 209, 223, 336/229; 174/138 R, 138 E, 138 F References Cited FOREIGN PATENTS OR APPLICATIONS 12/1959 Australia 174/138 E Primary ExaminerThomas J. Kozma Attorney, Agent, or FirmVale P. Myles [57] ABSTRACT End caps for the primary winding of an instrument transformer have a radius to relieve the electrical stress at the sharp edges of the primary. The end caps are provided with recesses to receive the primary leads and also have other recesses for locating the primary in a mold for encapsulating the instrument transformer. Lugs or tongues are provided at the inner edge of the end caps to support the winding during molding. Prior to molding, a conducting tape is attached to one primary lead and wound around the end caps.

2 Claims, 5 Drawing Figures rv US. Patent Dec. 9, 1975 3,925,7

This invention relates to instrument transformers, and more particularly, to end caps for the primary winding of instrument transformers.

In many instrument transformers the core and coil members are molded in an electrical insulation mate rial that forms both the insulation of the transformer and the exteriorcasing thereof. See, for example, U.S. Pat. No. 2,997,526. In these dry-type instrument transformers, often the primary winding is formed of one or more turns of copper or aluminum foil. This type of primary winding has led to two problems. One is the problem of the electrical stresses on the insulation which is caused by the sharp edges of the foil winding. The other is the tendency of the foil winding to collapse or become misshapened during the molding or encapsulation of the core and coil in the electrical insulation material.

It is, therefore, a primary object of this invention to provide a foil wound primary winding witha support means to give mechanical strength to such winding.

It is a further object of this invention to provide support means in the form of end caps for a foil wound primary winding, such end caps being provided with internal and external radii to relieve electrical stresses.

SUMMARY OF THE INVENTION In carrying out this invention in a preferred form, disk-shaped end caps are provided for foil wound windings. Each end cap has an internal and an external radius which relieves the sharp edges of the foil winding. Conducting tape which electrically engages one primary lead is wound about the exterior surface of the disk-shaped end caps. Each end cap is also provided with a plurality of tongues or lugs which snugly fit into the internal opening or window of the foil winding. As an additional feature of the invention, the end caps are provided with a plurality of recesses for locating the foil winding in a mold by mold pins during the molding operation.

The invention which is sought to be protected will be particularly pointed out and distinctly claimed in the claims appended hereto. However, it is believed that this invention and the manner in which its various objects and advantages are obtained, as well as other objects and advantages thereof, will be better understood by reference to the following detailed description of a preferred embodiment when considered with the accompanying drawing.-

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a foil winding having the preferred form of end caps of this invention mounted thereon;

FIG. 2 is a front plan view, on an enlarged scale, of the preferred form of end caps of this invention;

FIG. 3 is a side view of the end caps shown in FIG. 2;

FIG. 4 is a partial sectional view taken on the line 4 4 of FIG. 1, on the same scale as FIG. 2; and

FIG. 5 is a sectional view taken on line 55 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, in which like numerals 5 are used to indicate likeparts throughout the various views thereofgthere. is shown in FIG. 1, a composite primary foil winding 10 comprising a plurality of turns of a foil 12 (see FIG. 4) secured by band 14. Leads 16 and 18 are secured to the opposite ends (not shown) of the winding 10; the leads l6, 18 in turn being secured to the transformer leads 20, 22. Obviously, leads l6 and 18 may be secured to winding 10 and leads 20, 22 in any desired manner; such as brazing, bolting and the like, which are well known in the art.

As is well understood, when a winding such as 10 of foil 12 is encapsulated or molded in a dry-type instrument transformer the sharp edges 24 and 26 on the inner and outer diameter of the winding causes an electrical stress on the insulation surrounding the foil winding. To relieve this electrical stress, end caps 28, 30 are placed on opposite sides of the winding of foil 12 and have a radius such as radius 32, 34 on end cap 28 and radius 36, 38 on end cap 30 (see FIG. 5) to eliminate the effect of the sharp edges 24, 26 and eliminate these electrical stresses. Of course, the exterior of the composite winding 10 is wrapped in electrical conducting tape 40, which in turn is electrically connected to either primary winding leads 16 or 18. In FIGS. 1 and 4, only a few turns of electrical conducting tape 40 are shown so as to improve the overall exposition of the invention.

FIGS. 2 and 3 show respectively the front and side views of a preferred form of the end caps of this invention. It will be understood that while only end cap 30 is shown in FIGS. 2 and 3 that end cap 28 is of the identical shape. Thus, the description of one applies to both. The end caps 28 and 30 are preferably formed of a (polycarbonate resin) material to provide the desired mechanical strength to the primary winding. Obviously, other resinous material of appropriate mechanical strength could be used.

As is shown in FIGS. 2 and 3, molded end cap 30 is provided with a plurality of tongues 42, 44, 46 and 48. These tongues or lugs fit snugly within the interior of the winding of foil 12 as is clearly evident from FIGS. 1 and 4. As will be understood, these tongues support the winding of foil 12, insuring that it will maintain its shape during the molding operation. As can be seen in FIGS. 2 and 4, slots 50 and 52 are provided at the inner surface of end cap 30 to allow the leads l6 and 18 to be brought out from the winding. Further, recesses 54 and 56 are provided on the exterior of end cap 30. These recesses are utilized in conjunction with mold pins to firmly mount the composite primary winding 10 in a mold during the molding or encapsulation of the composite primary winding.

While there has been shown and described the present preferred embodiment of the end caps of this invention and the composite primary winding utilizing such end caps, it will be understood by those skilled in the art that various changes may be made in construction without departing from the spirit and scope of the invention as it is defined in the appended claims.

What is claimed as new and which it is desired to secure by Letters Patent of the United States is:

1. A composite primary foil winding comprising at least one turn of an electrical conducting foil, a pair of molded end caps mounted on opposite sides of said foil winding, each said end cap provided with an internal and an external radius to relieve electrical stress at the sharp corners of said foil winding, and each said end cap having a plurality of tongues snugly fitting within the central opening of said foil winding to provide mechanical strength to said foil winding, and an electrical conducting tape wrapped about the exterior surfaces of said end caps.

2 A composite electrical foil winding as set forth in claim 1, in which each of said end caps is provided with a plurality of recesses for mounting said composite foil winding in a mold. 

1. A composite primary foil winding comprising at least one turn of an electrical conducting foil, a pair of molded end caps mounted on opposite sides of said foil winding, each said end cap provided with an internal and an external radius to relieve electrical stress at the sharp corners of said foil winding, and each said end cap having a plurality of tongues snugly fitting within the central opening of said foil winding to provide mechanical strength to said foil winding, and an electrical conducting tape wrapped about the exterior surfaces of said end caps.
 2. A composite electrical foil winding as set forth in claim 1, in which each of said end caps is provided with a plurality of recesses for mounting said composite foil winding in a mold. 